package org.apache.lucene.search.function;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.FieldCache;
import org.apache.lucene.search.function.DocValues;

import java.io.IOException;

/**
 * Expert: obtains float field values from the 
 * {@link org.apache.lucene.search.FieldCache FieldCache}
 * using <code>getFloats()</code> and makes those values 
 * available as other numeric types, casting as needed.
 * 
 * @lucene.experimental
 * 
 * @see org.apache.lucene.search.function.FieldCacheSource for requirements 
 * on the field.
 *
 * <p><b>NOTE</b>: with the switch in 2.9 to segment-based
 * searching, if {@link #getValues} is invoked with a
 * composite (multi-segment) reader, this can easily cause
 * double RAM usage for the values in the FieldCache.  It's
 * best to switch your application to pass only atomic
 * (single segment) readers to this API.</p>
 */
public class FloatFieldSource extends FieldCacheSource {
    private FieldCache.FloatParser parser;

    /**
     * Create a cached float field source with default string-to-float parser. 
     */
    public FloatFieldSource(String field) {
        this(field, null);
    }

    /**
     * Create a cached float field source with a specific string-to-float parser. 
     */
    public FloatFieldSource(String field, FieldCache.FloatParser parser) {
        super(field);
        this.parser = parser;
    }

    /*(non-Javadoc) @see org.apache.lucene.search.function.ValueSource#description() */
    @Override
    public String description() {
        return "float(" + super.description() + ')';
    }

    /*(non-Javadoc) @see org.apache.lucene.search.function.FieldCacheSource#getCachedValues(org.apache.lucene.search.FieldCache, java.lang.String, org.apache.lucene.index.IndexReader) */
    @Override
    public DocValues getCachedFieldValues(FieldCache cache, String field, IndexReader reader) throws IOException {
        final float[] arr = cache.getFloats(reader, field, parser);
        return new DocValues() {
            /*(non-Javadoc) @see org.apache.lucene.search.function.DocValues#floatVal(int) */
            @Override
            public float floatVal(int doc) {
                return arr[doc];
            }

            /*(non-Javadoc) @see org.apache.lucene.search.function.DocValues#toString(int) */
            @Override
            public String toString(int doc) {
                return description() + '=' + arr[doc];
            }

            /*(non-Javadoc) @see org.apache.lucene.search.function.DocValues#getInnerArray() */
            @Override
            Object getInnerArray() {
                return arr;
            }
        };
    }

    /*(non-Javadoc) @see org.apache.lucene.search.function.FieldCacheSource#cachedFieldSourceEquals(org.apache.lucene.search.function.FieldCacheSource) */
    @Override
    public boolean cachedFieldSourceEquals(FieldCacheSource o) {
        if (o.getClass() != FloatFieldSource.class) {
            return false;
        }
        FloatFieldSource other = (FloatFieldSource) o;
        return this.parser == null ? other.parser == null : this.parser.getClass() == other.parser.getClass();
    }

    /*(non-Javadoc) @see org.apache.lucene.search.function.FieldCacheSource#cachedFieldSourceHashCode() */
    @Override
    public int cachedFieldSourceHashCode() {
        return parser == null ? Float.class.hashCode() : parser.getClass().hashCode();
    }
}